Possible associations of gender, age, and participation in volunteer activities with altruistic behavior of Chinese adolescents were investigated. A representative sample of 1,105 Hong Kong Chinese adolescents (457 boys, 648 girls) were recruited from 20 schools. Results of multiple regression analyses indicated that there was a positive age effect on altruistic behavior. In addition, a positive association between self-reported altruistic behavior and frequency of participation in volunteer activities was found. No gender differences were found.